Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$169.41	8.608%	$183.9928	$183.99	$184.00	$184.00
Purchase #2	$154.84	3.638%	$160.4731	$160.47	$160.45	$160.50
Purchase #3	$79.60	13.349%	$90.2258	$90.23	$90.25	$90.20
Purchase #4	$216.32	4.135%	$225.2648	$225.26	$225.25	$225.30
Purchase #5	$106.37	5.238%	$111.9417	$111.94	$111.95	$111.90
Purchase #6	$97.89	6.748%	$104.4956	$104.50	$104.50	$104.50
Purchase #7	$150.92	11.669%	$168.5309	$168.53	$168.55	$168.50
7 purchase totals =	$975.35		$1,044.9247	$1,044.92	$1,044.95	$1,044.90